Modern agricultural implements, such as chisel plows, disc cultivators or planters have become larger with the increasing horsepower in tractors so that in a single pass, a much wider swath of soil is worked or planted. The increasing width of agricultural implements has made it difficult to transport the implements through field gates or over the road from field to field. Provisions have been made to permit the implements to fold for transport.
One common folding configuration provides for a center frame section which is mounted to the tractor and first and second outboard frame sections or "wings".
The center frame section and the outer frame sections each include an elongated mounting bar (sometimes referred to as a "toolbar") on which the working tools or, in the case of a planter, the row units are mounted.
When the implement is in the field or use position, the wings are lowered so that the wing mounting bars are generally horizontal and aligned with the mounting bar of the center frame section. A hinge mechanism interconnects each wing mounting bar with the associated outboard end of the mounting bar of the center frame section. In the use position, the hinge sections must permit the wing sections to move up and down or "flex" to conform to variations in ground contour during use.
When it is desired to transport the implement, the wing sections are folded to vertical positions by the hinge assemblies, which include hydraulic cylinders providing the power necessary to raise the wing sections to the folded position.
In the transport position, the mounting bars are normally in generally vertical positions, at least for the kind of implement of the type with which the present invention is concerned, although other configurations are known.
In a vertically folding implement frame of this type, when the wing mounting bars are in the folded, vertical position, the tools or planter row units remain mounted to the wing sections and extend outwardly of their associated mounting bars. Thus, the weight of the tools or row units normally has a tendency to force the wing sections back to the horizontal position. In some prior art hinge assemblies for vertically folding implement frames, it is possible that if hydraulic pressure is lost in one or both of the hydraulic cylinders holding the wing sections in their transport position, the weight of the tools or row units would cause the wing section to drop.
It is obviously undesirable to permit a wing section to fall because of the potential damage to the tools on the wing, and also because the farmer may be transporting the implement through a narrow passage or gate or into a barn or storage shed, and further damage could be caused. Thus, implements of this type normally have mechanical locks for locking the wings in the vertical position so there is no possibility of having the wing section fall when it is mechanically locked in the raised position. Mechanical locks are used for road transport, but it is inconvenient and time-consuming to lock the wings in the raised position every time the wing sections are folded. Locking is not always necessary for safety reasons, particularly when the farmer may be planting end rows or transporting his planter from one section of a field to another section of the same field and it is not necessary to travel over a road.
The present invention provides an improved hinge assembly for interconnecting the wing section of a vertically folding agricultural implement frame with the center section of the implement frame. The hinge assembly includes a hydraulic cylinder pivotally connected at the butt end to the center frame section and at its rod end to a pivot juncture between a locator or idler link and a push link. The other end of the push link is pivotally connected to the wing frame, and the other end of the locator link is pivotally connected to the center frame section.
When the hydraulic cylinder is extended, the push link forces the wing section to rotate in a vertical motion about a horizontal axis parallel to the direction of travel through an arc of approximately 90.degree. until the mounting bar of the wing is in a generally vertical position. The locator link guides the movement of the pivot juncture (and thus, the movement of the rod end of the cylinder as well as of the inboard end of the push link). The hinge assembly is designed such that when the hydraulic cylinder is in a fully-extended position, the pivot juncture passes to an over-center position--that is, the pivot juncture passes through a line extending between the axis of the pivot connection of the push link and the wing frame and the pivot axis of the idler link and the center frame. A stop is provided so that the movement of the pivot juncture is limited to prevent further motion of the pivot juncture beyond the desired over-center position. In this manner, the force of the wing section is transmitted through the push link to the locator link and the locator link acts as a crank-stop. The weight of the wing section acts to lock the hinge assembly in the raised position, and it is necessary to retract the hydraulic cylinder before the wing section can be lowered again.
Thus, when the wing section is raised to the folded position, the hinge assembly locks the wing section, and the wing section cannot be lowered even if hydraulic pressure to the cylinder is lost.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.